The present invention relates to a new and improved method and apparatus for casting a metal article. A mold for the metal article may be moved into a fluidized bed to promote heat transfer from the mold. The mold for the metal article may be positioned adjacent to one or more heat sinks to promote heat transfer from the mold.
An apparatus for molding a metal article is disclosed in U.S. Pat. No. 4,573,516. This apparatus includes a furnace assembly and a mold filled with molten metal. The apparatus also includes a fluidized bed which is disposed below the furnace assembly. The mold is lowered from the furnace assembly into the fluidized bed to effect solidification of the molten metal in the mold.
Another apparatus for use in casting metal articles and utilizing a fluidized bed is disclosed in U.S. Pat. No. 6,035,924. This apparatus includes a furnace assembly from which a mold containing molten metal is lowered into a fluidized bed. A layer of hollow spherical bodies is disposed on an upper end portion of the fluidized bed.
Another apparatus for use in casting metal articles is disclosed in U.S. Pat. No. 3,810,504. This apparatus includes a furnace assembly from which a mold containing molten metal is lowered into a space between inner and outer heat sinks. The mold may be constructed so as to have either an annular array of article mold cavities or an annular mold cavity.
The present invention relates to a new and improved method and apparatus for use in casting a metal article. During casting of the metal article, a mold may be moved into a fluidized bed. The fluidized bed may have an annular configuration. If the mold is moved into a fluidized bed, molten metal in the mold is solidified as the mold moves into the fluidized bed.
In one specific instance, the mold is raised into a furnace assembly where the mold is filled with molten metal. A container holding a fluidized bed is moved to a raised position adjacent to the furnace assembly. The mold is lowered into the fluidized bed in the container. The container is lowered.
When the mold is moved into a fluidized bed, a central portion of a container for the fluidized bed may extend around a passage through which a support member for the mold extends. The central portion of the container prevents particulate in the fluidized bed from engaging the mold support member. This may eliminate the need for a seal around the mold support member. Inner and/or outer side walls of the container may be formed as heat sinks to promote heat transfer from the mold.
A stirrer member may be provided in the fluidized bed to promote distribution of particulate in a flow of gas through the fluidized bed. A support for the mold may have a plurality of openings to enable gas and particulate to flow through the support for the mold. Fluid may be conducted from the support for the mold to promote fluidization of particulate. Fluidization of the particulate may also be promoted by conducting gas at different pressures into different locations in the fluidized bed.
The mold may be constructed with a central portion and a peripheral portion in which a plurality of article mold cavities are disposed. The mold may be supported by engaging the central portion of the mold. The peripheral portion of the mold may be spaced from the support to facilitate heat transfer from the article mold cavities. The central portion of the mold may be suspended from an upwardly extending support. The mold may be supported by a downwardly extending support.
The side walls of the container for the fluidized bed may be configured so as to effect a change in the speed of movement, through the fluidized bed, of the gas in which the particulate is suspended. Baffles may be provided in association with the fluidized bed to deflect portions of the flow of fluidized material in the bed. Bellows, which may be flexible sleeves, are advantageously associated with apparatus which extends into the fluidized bed to minimize exposure of seals to the particulate in the fluidized bed. However, the bellows and/or seals may be eliminated when a central portion of the container at least partially defines a passage through the fluidized bed.
When the molten metal solidifies in the mold, the molten metal may be solidified with a cellular front which is free of dendrites. By solidifying the molten metal with a cellular front which is free of dendrites, the characteristics of the resulting casting are enhanced.
It has been established that satisfactory solidification of molten metal in a mold may be obtained when a flow of gas is conducted through the fluidized bed at a flow rate of between 5 and 100 cubic feet per hour for each square foot of the fluidized bed in a horizontal plane. The upper portion of the fluidized bed may be exposed to a fluid pressure of between 6xc3x9710xe2x88x924 atmosphere to 1.0 atmosphere. The maximum temperature at the upper portion of the fluidized bed may vary within a range of 2,500 degrees Fahrenheit and 3,000 degrees Fahrenheit.
It should be understood that any one of the features mentioned above and/or additional features may be utilized by itself or in combination with other features of the invention. It should also be understood that the invention is not to be limited to any one of the specific embodiments disclosed herein. This is because there are many different ways in which the various features of the invention may be used together or separately and in which they may be changed from the specific embodiments disclosed herein.